From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 13EC8EB64D7 for ; Fri, 30 Jun 2023 16:10:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A0EE08E0033; Fri, 30 Jun 2023 12:10:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9BF558E000F; Fri, 30 Jun 2023 12:10:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8AE458E0033; Fri, 30 Jun 2023 12:10:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 7C0658E000F for ; Fri, 30 Jun 2023 12:10:51 -0400 (EDT) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 3A248160555 for ; Fri, 30 Jun 2023 16:10:51 +0000 (UTC) X-FDA: 80959902702.03.C6D5CE7 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf04.hostedemail.com (Postfix) with ESMTP id 65C8F40027 for ; Fri, 30 Jun 2023 16:10:48 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=dq19zYXM; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf04.hostedemail.com: domain of nathan@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=nathan@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1688141448; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=VmI3so5b9Uv275rlHS6GxiDuimwR9UYHvzNYBjFZRg8=; b=Vd6PVR7xs8WYAwBKPTd8ib1oOZ71kK7kioRknVPkxR+umhiNOjBNkVXqdjYEXfDKrAmEuu OrZzpRF7rnkBfWTP/pXSDp7RGWKS5pJFd2Y0tDpt/G1qfsKjNxi6cUE0DHuycI+wDfyssz gTIDOGkp6no2KEi3bKrQdXLUXgIN3Wc= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=dq19zYXM; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf04.hostedemail.com: domain of nathan@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=nathan@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1688141448; a=rsa-sha256; cv=none; b=DH8LbMS6sreYCX+e0yXnzkvyNp7tREL5PbrwjEZBIFJu8qAB0kvw8TCAt3THTs71xMroPc nbawk0166b1qEEXYXAVMK853mNhKru+42n+sbSu58BCwNSyYMZCJAfs4YswLMss6IQJXUU 3ROgPhU3IcE95eLkf52zq3e8d/80sNw= Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 61E786178A; Fri, 30 Jun 2023 16:10:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A10FFC433C8; Fri, 30 Jun 2023 16:10:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1688141446; bh=65l3uxIkPZ2teqmqxsQP31N9JJV0zpume1JU++/LnAI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dq19zYXMqF5Odo1p5GFM9j0nL2LZbW9qCerBaCPD8Oh6xhb8sATyqGZUXXM9H9unc eRT4kJN5byP86KaZkhnglG8iXD2T0YGHFmLTrQrj3hvDckwk2jEc9VSNh2t9S/gxtJ 0Dx4t8ni/nfwppvYEAAUncwVBPXcvfHU7DJrXLg3fET5wHbfrq5/jlIApbGWZ57tzU idF/ITTbqiOgio39UFgA608R07VkW9agfG8sIhl0EcPgKzi45w4hBlJ3dOUUDCHDjR kxdILhNhzz3xw0Nm/HMh5YNMZKfqYFnsjYN/yyZRKtIIckltFJimgsA/AudefjbpOn X66t6KgUID+dQ== Date: Fri, 30 Jun 2023 09:10:43 -0700 From: Nathan Chancellor To: Jakub Kicinski Cc: David Howells , Aurelien Aptel , netdev@vger.kernel.org, Alexander Duyck , "David S. Miller" , Eric Dumazet , Paolo Abeni , Willem de Bruijn , David Ahern , Matthew Wilcox , Jens Axboe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sagi Grimberg , Willem de Bruijn , Keith Busch , Jens Axboe , Christoph Hellwig , Chaitanya Kulkarni , linux-nvme@lists.infradead.org, llvm@lists.linux.dev Subject: Re: [PATCH net-next v3 10/18] nvme/host: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage Message-ID: <20230630161043.GA2902645@dev-arch.thelio-3990X> References: <253mt0il43o.fsf@mtr-vdi-124.i-did-not-set--mail-host-address--so-tickle-me> <20230620145338.1300897-1-dhowells@redhat.com> <20230620145338.1300897-11-dhowells@redhat.com> <58466.1688074499@warthog.procyon.org.uk> <20230629164318.44f45caf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230629164318.44f45caf@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 65C8F40027 X-Stat-Signature: egtb4sc8jgy1hdm6nf7xejf8etiaahep X-HE-Tag: 1688141448-244227 X-HE-Meta: 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 MXewNYKe 9hcYckhX8NNH0Pl/dWltGxNIxxZK44GoK0A3wXA2nu0gs2gcE6r+B+PmcsAFCMkLFY4Gf1l5MJBD/86DWSqlzufmj9+bPys5FRf6yhNI/BDs+I3eaAIMLKoA1c/dBmDT8We3U5D0kQAuhG54MJdDGSKjZ/Jght4oElNvUVukAyIc1ZEyld3j8YKIPt/U9XTpoA6lyqhR/qFOTlm2L4ZLNt1Yox1kY8ENc4JGPu2vJy7fkPQ99Igg2jawXPR35eQceFJfA0AdlkIypYXqoepgg1W2AGK8xuANv0199DPw+heBae2OzVUlNUtBsc1eG8fQPd9mzvkMEHvKUFSgXAY1ahAX/aqGVEjV458bJ3pRGM8aptdY38C5FNnKgF+A64R9ITnJnWDU1MOVDgrxOItBqVuZlTpTwiprG3CphhEEMwTzTVqA9Atdeztu00C7YbcHvk0woH7FA/f7SJ1CEWplJwfq4kg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 29, 2023 at 04:43:18PM -0700, Jakub Kicinski wrote: > On Thu, 29 Jun 2023 22:34:59 +0100 David Howells wrote: > > if (!sendpage_ok(page)) > > - msg.msg_flags &= ~MSG_SPLICE_PAGES, > > + msg.msg_flags &= ~MSG_SPLICE_PAGES; > > 😵️ > > Let me CC llvm@ in case someone's there is willing to make > the compiler warn about this. > Turns out clang already has a warning for this, -Wcomma: drivers/nvme/host/tcp.c:1017:38: error: possible misuse of comma operator here [-Werror,-Wcomma] 1017 | msg.msg_flags &= ~MSG_SPLICE_PAGES, | ^ drivers/nvme/host/tcp.c:1017:4: note: cast expression to void to silence warning 1017 | msg.msg_flags &= ~MSG_SPLICE_PAGES, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | (void)( ) 1 error generated. Let me do some wider build testing to see if it is viable to turn this on for the whole kernel because it seems worth it, at least in this case. There are a lot of cases where a warning won't be emitted (see the original upstream review for a list: https://reviews.llvm.org/D3976) but something is better than nothing, right? :) Cheers, Nathan